JP4132987B2 - How to create a three-dimensional gear model - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for creating a three-dimensional model of a gear, and more particularly to a method for efficiently creating a three-dimensional model of a gear with high tooth surface accuracy.
[0002]
[Prior art]
With the spread and development of computers, machine design is shifting from 2D CAD (Computer Aided Design) to 3D CAD. One of the problems in 3D CAD is a method of inputting a shape. In general, special skills are required to construct a three-dimensional model on a CAD system, and this operation takes a very long time. In order to solve such an input problem, reverse engineering techniques have begun to attract attention. Specifically, a model is constructed in a CAD system by inputting surface shape data of an object for which a three-dimensional model is desired to be constructed into the CAD.
[0003]
Conventionally, a three-dimensional shape measuring apparatus is known as means for creating surface shape data of an object. The three-dimensional shape measuring apparatus scans the surface of an object by, for example, a non-contact laser method, and creates three-dimensional point group data. By importing this point cloud data into the CAD system and forming a curved surface that matches the point cloud data, a three-dimensional model can be constructed on the CAD system.
[0004]
By performing CAE (Computer Aided Engineering) analysis on such a three-dimensional model, it is possible to evaluate the performance of components and the like before actual machining. For example, Japanese Patent Laid-Open No. 10-627 discloses a product production method including a process of producing a design model based on CAD three-dimensional data and evaluating the design model to obtain new three-dimensional data. ing. According to this method, design evaluation and functional evaluation can be performed before manufacturing a simple mold for manufacturing a product, so that the research and development period from design development to manufacturing can be shortened. It is said.
[0005]
[Problems to be solved by the invention]
The hypoid gear used for driving the rear axle of an automobile has smooth power transmission and excellent noise reduction. Conventionally, even if there was a hypoid gear with excellent performance, it was difficult to specify the parameters of the processing machine from the tooth profile of the actual machine in order to create the same gear. However, due to advances in three-dimensional measurement technology, it is also possible to create hypoid gears that have the same performance as the model by measuring hypoid gear teeth that become models, converting their data into data, and passing the data to NC machine tools. It is possible.
[0006]
It is known that the performance of the gear, particularly the noise, varies greatly depending on the difference in the submicron order shape of the gear tooth surface. Therefore, when creating a three-dimensional model of such a gear and performing characteristic analysis by CAE, or converting it to NC data, it is necessary to measure the gear three-dimensionally with submicron accuracy. However, when measurement is performed with such high accuracy, there is a problem that not only a long time is required for the measurement, but also the data size becomes enormous.
[0007]
In view of the above problems, an object of the present invention is to provide a method for efficiently creating a three-dimensional solid model of a gear that requires particularly high accuracy, such as a hypoid gear.
[0008]
[Means for Solving the Problems]
The present invention combines the solid data of the gear material before processing created by solid modeling and the like and the tooth surface data created by three-dimensional measurement to complete a three-dimensional model of the entire gear on the CAD system. Is the method.
[0009]
In one embodiment of the present invention, a process of creating solid data of a material before being processed into a gear, a process of obtaining a tooth surface data by three-dimensionally measuring a tooth surface shape of a gear that is a creation target of a three-dimensional model, and , Including a process of creating tooth surface solid data from the acquired tooth surface data, and a process of synthesizing the solid data of the material and the tooth surface solid data to complete solid data of the entire gear.
[0010]
According to this form, solid data is created using data acquired by 3D measurement for gear tooth surfaces that require high accuracy in creating a 3D model, while solid modeling etc. is used for parts that do not require accuracy. The solid data is created by the above, and these are combined to complete the solid data of the entire gear. Therefore, a three-dimensional model having the accuracy required for CAE analysis or the like can be created in a relatively short time.
[0011]
Note that the tooth surface data copied for the number of teeth may be directly combined with the material solid data without converting the tooth surface data into the tooth gap solid data.
[0012]
In another embodiment of the present invention, a set of tooth surface data is obtained by three-dimensionally measuring the tooth surface shape of both ends constituting one of the tooth grooves of the gear, and the solid data of the tooth groove is obtained from the tooth surface data. The tooth surface solid data is created by copying the solid data of the tooth gaps by the number of teeth of the gear.
[0013]
According to this embodiment, solid data is first created for only one tooth gap of the gear, and this is copied by the number of teeth, so the time required for creating the three-dimensional model is further shortened and the amount of data is also reduced. .
[0014]
In still another embodiment of the present invention, a rough shape of a tooth is input in advance, and a probe for three-dimensional measurement is moved along this shape.
[0015]
According to this embodiment, since the movement of the probe is accelerated, the time required for the three-dimensional measurement is shortened.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a diagram showing an overall configuration of a system suitable for carrying out a gear three-dimensional model creation method according to an embodiment of the present invention.
[0017]
The three-dimensional tooth profile measuring device 18 measures the shape of the tooth surface by bringing the probe into contact with the tooth surface of the gear to be a three-dimensional model creation target and moving the probe along the tooth surface as shown in FIG. Output 3D point cloud data. At this time, it is preferable that a rough shape of the tooth is input in advance, and the three-dimensional tooth profile measuring device 18 moves the probe while referring to this. This is because, for example, in a case where teeth are bent in a vortex like a hypoid gear, if there is no data to be used as a reference for probe movement, the measurement time increases, and the tooth surface where the probe or probe grip is adjacent. This is for avoiding this. Instead of the probe, the tooth surface may be irradiated with a laser, and the distance from the reflection time to the tooth surface may be calculated to obtain three-dimensional point group data.
[0018]
The point cloud data is sent to the surface data creation unit 22 through a preprocessing unit 20 that performs processing such as deleting unnecessary points. The surface data creation unit 22 creates surface data from the point cloud data and sends it to the three-dimensional CAD system 30.
[0019]
Specifically, the three-dimensional CAD system 30 includes a central processing unit, a mass storage device, an input device, a display device, and the like. In FIG. It is represented as a functional block composed of the unit 28. The surface data sent from the surface data creation unit 22 is sequentially processed by these units and converted into solid data. A variety of CAD systems 30 can be used, but it is necessary to employ boundary representations as a representation format of three-dimensional data.
[0020]
In FIG. 1, the preprocessing unit 20, the surface data creation unit 22, and the CAD system 30 are represented as separate devices, but applications having the respective functions are stored in a single computer. A three-dimensional model creation system can also be realized. Also, a three-dimensional model creation system can be realized by connecting computers equipped with the respective applications via a network such as a LAN.
[0021]
Various applications having the functions of the preprocessing unit 20, the surface data creation unit 22, or the CAD system 30 are realized. As is well known to those skilled in the art, data migration between such applications often involves format conversion, but is not individually mentioned in the following description. It will be understood that the present invention is applicable regardless of the type of application or format, since translators that perform format conversion can be created by those skilled in the art.
[0022]
Next, the process of the gear three-dimensional model creation method according to the embodiment of the present invention will be described with reference to the flowchart of FIG. In this embodiment, firstly, the solid surface of the tooth gap (that is, the portion removed from the original material during processing) is created, and the tooth surface is obtained by subtracting the solid data of the tooth gap from the solid data of the separately created material. Reproduce the entire three-dimensional shape.
[0023]
First, using the three-dimensional tooth profile measuring device 18, the tooth surface of the gear that is the object of creation of the three-dimensional model is measured (S40). At this time, instead of measuring all the teeth, one of the tooth gaps is selected, and only the shapes of the tooth surfaces on both sides (that is, the side surfaces of the teeth) constituting the tooth gap are measured. The measured shape is sent to the preprocessing unit 20 as point cloud data and subjected to preprocessing such as alignment and deletion of unnecessary point cloud data (S42).
[0024]
Next, the surface data creation unit 22 creates surface data from the preprocessed point cloud data (S44). There are various methods for creating surface data from point cloud data. In the present embodiment, the noise included in the point cloud data is removed, and data is thinned out appropriately to reduce the calculation time, and then polygonization is executed. Then, the defective polygon is deleted, smoothed, hole-filled, edge corrected, and the like, the feature line of the polygon is extracted, and the surface configuration is arranged so that it can be expressed by surface data. Then, a grid is created for each face, and surface data is created based on the grid. The series of processes described above can be performed using known surface automatic generation software. The surface data is held in a mathematical expression such as a Bezier curved surface or a NURBS curved surface.
[0025]
The method of creating surface data from polygons is preferable because a highly accurate curved surface can be created for point cloud data, but in another embodiment, cross-section information (wire frame) is first generated from point cloud data, and then Surfaces can also be created to connect each section in succession.
[0026]
Since the surface data is only the geometric information of the object surface, in order to build a solid model that can completely represent a solid, the surface data must first be connected to face data that represents a continuous surface. However, when face data is created from surface data, a topological space may occur between adjacent face data. This is a phenomenon caused by a difference in tolerance (tolerance) at the time of data conversion because adjacent surface data are not in a strict sense. Conventionally, a process of selecting a boundary line between face data and merging to make a closed space (hereinafter referred to as “close process”) has been performed. The closing process may be performed automatically, but manual correction is also required. For this reason, in the creation of the three-dimensional model, the proportion of time required for the closing process is very large.
[0027]
In this embodiment, assuming that all the surface data is closed, face data that is closed directly from the surface data is created (S46), so the model creation time is reduced.
[0028]
The created face data is turned into a volume by the volume creation unit 26 (48), and solid data is created by the solid data creation unit 28 (S50). This process is well known and will not be described in detail.
[0029]
Once solid data for one tooth gap has been created in this way, the solid data for the tooth gap is then copied around the center axis of the gear at equal intervals for the number of gear teeth for which the 3D model is to be created. (S52). FIG. 4A is an example of tooth gap solid data when the model creation target is a hypoid gear.
[0030]
Next, solid data of the gear material is created (S54). For example, the inner and outer circumferences of the gear to be modeled may be measured by the three-dimensional tooth profile measuring device 18 and solid data may be created from this data as described above. In this embodiment, detailed measurement of the gear is performed. The solid data of the material is created by well-known solid modeling by the Boolean operation of the primitive without performing the above. This is because the accuracy of the tooth surface greatly affects the performance of the gear, but the parts other than the tooth surface have little effect on the performance even if the accuracy is not so high. It is not necessary to do. When creating solid data of materials by solid modeling, the material shape is a combination of simple shapes such as cylinders and cones, so the data volume is very small compared to creating solid data from 3D measurement data Please be careful.
[0031]
Then, the solid data of the material created as described above and the solid data of the tooth gap created in step S52 are synthesized (S56). Specifically, as shown in FIG. 4, the tooth gap solid data (FIG. 4 (a)) is subtracted from the material solid data (FIG. 4 (b)) with the tooth apex as a reference, and the entire gear is Complete the solid data (Fig. 4 (c)). The tooth surface of the solid data of the entire gear is the same as that obtained by converting the tooth surface shape into solid data instead of the tooth gap.
[0032]
As another embodiment, the tooth surface data copied for the number of teeth may be directly combined with the material solid data without converting the tooth surface data into the tooth gap solid data.
[0033]
The generated solid data of the entire gear can be used for strength analysis and dynamic motion analysis by the CAE system, or used for copying the gear to be modeled by converting it to NC data and sending it to the NC machine tool. You can also. If it does in this way, it will become possible to reverse-engineer the gear whose specification is unknown and to analyze the gear.
[0034]
The solid data for the entire gear created as described above is a copy of the solid data for one tooth gap for the number of teeth and is combined with a material with a small amount of data. Compared to solid data created by three-dimensional measurement, the amount of data is extremely small and the measurement time is shortened. Thus, it is one of the features of the present invention that the solid models having different accuracy are synthesized according to the importance of accuracy.
[0035]
As mentioned above, although one Embodiment of this invention was described, this invention is not restricted to this form, A various deformation | transformation, change, and improvement can be performed. For example, the hypoid gear has been described as an example, but other gears such as an involute gear and a worm gear can be applied with a slight improvement. If more detailed data is required according to the purpose of CAE analysis, it is of course possible to measure all tooth surfaces and convert them into data.
[0036]
【The invention's effect】
According to the present invention, a three-dimensional model of a gear with high tooth surface accuracy can be created in a short time and with a small amount of data.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram of a system adapted to a gear three-dimensional model creation method according to the present invention.
FIG. 2 is a flowchart illustrating a method for creating a three-dimensional gear model according to the present invention.
FIG. 3 is a diagram showing measurement by a three-dimensional tooth profile measuring apparatus.
FIG. 4 is a diagram showing composition of material solid data and tooth gap solid data.
[Explanation of symbols]
18 Three-dimensional tooth profile measuring device 20 Preprocessing unit 22 Surface data creation unit 24 Face data creation unit 28 Solid data creation unit 30 CAD system

Claims (3)

A method for creating a three-dimensional model of a gear on a CAD system,
The process of creating solid data of the material before being processed into gears,
The process of obtaining the tooth surface data by three-dimensionally measuring the tooth surface shape of the gear for which the 3D model is to be created,
The process of creating tooth surface solid data from the acquired tooth surface data,
Look including the the steps of completing the solid data for the entire gear by combining the tooth surface solid data and solid data of the material,
Three-dimensional measurement of the tooth surface shape on both sides of one of the gear tooth spaces is obtained to obtain a set of tooth surface data, and solid data of the tooth grooves is created from the tooth surface data. The tooth surface solid data is created by copying data by the number of gear teeth.
3D model creation method for gears. The method for three-dimensional modeling of a gear according to claim 1 , wherein a rough shape of a tooth is input in advance, and a probe for performing three-dimensional measurement is moved along the shape. The gear is a hypoid gear, three-dimensional modeling method of the gear according to claim 1 or 2.

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